Locksmith Job, Not a Mechanic Job
Ignition cylinders contain small metal wafers that wear down over years of use, the same way a door lock does, and worn wafers are one of the most common reasons a key becomes hard to turn or stops working altogether. This is mechanical lock wear, not an engine or electrical fault, which means it falls squarely under locksmith work. Bringing the car to a mechanic first often means an unnecessary diagnostic fee before you're referred to a locksmith anyway.